netdev - Re: [PATCH] tun: orphan an skb on tx

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Message-ID: <20100413204307.GC3582@redhat.com>
Date:	Tue, 13 Apr 2010 23:43:07 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Jan Kiszka <jan.kiszka@...mens.com>,
	"David S. Miller" <davem@...emloft.net>,
	Herbert Xu <herbert@...dor.hengli.com.au>,
	Paul Moore <paul.moore@...com>,
	David Woodhouse <David.Woodhouse@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	qemu-devel <qemu-devel@...gnu.org>
Subject: Re: [PATCH] tun: orphan an skb on tx

On Tue, Apr 13, 2010 at 10:38:06PM +0200, Eric Dumazet wrote:
> Le mardi 13 avril 2010 à 23:25 +0300, Michael S. Tsirkin a écrit :
> > On Tue, Apr 13, 2010 at 08:31:03PM +0200, Eric Dumazet wrote:
> > > Le mardi 13 avril 2010 à 20:39 +0300, Michael S. Tsirkin a écrit :
> > > 
> > > > > When a socket with inflight tx packets is closed, we dont block the
> > > > > close, we only delay the socket freeing once all packets were delivered
> > > > > and freed.
> > > > > 
> > > > 
> > > > Which is wrong, since this is under userspace control, so you get
> > > > unkillable processes.
> > > > 
> > > 
> > > We do not get unkillable processes, at least with sockets I was thinking
> > > about (TCP/UDP ones).
> > > 
> > > Maybe tun sockets can behave the same ?
> > 
> > Looks like that's what my patch does: ip_rcv seems to call
> > skb_orphan too.
> 
> Well, I was speaking of tx side, you speak of receiving side.

Point is, both ip_rcv and my patch call skb_orphan.

> An external flood (coming from another domain) is another problem.
> 
> A sender might flood the 'network' inside our domain. How can we
> reasonably limit the sender ?
> 
> Maybe the answer is 'We can not', but it should be stated somewhere, so
> that someone can address this point later.
> 

And whatever's done should ideally work for tap to IP
and IP to IP sockets as well, not just tap to tap.

-- 
MST
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